Abstract: Taking 5083 aluminum alloy MIG welded joint as the research object, the microstructure, microhardness, high-cycle fatigue property and fatigue fracture characteristics were studied. The results show that, there are dense discontinuous precipitates in weld zone of the welded joint. Compared with that of the base material, the precipitates in the welded joint are distributed more intensively and the size is coarser.However, the hardness of the welded joint is equivalent to that of the base material, which is mainly related to the enhancement of precipitation strengthening effect and disappearance of deformation strengthening effect. The 10⁷ cycles fatigue strength of the welded joint is 46.4 MPa. There are many fatigue sources for the welded joint, and the fatigue cracks initiate at the welding defects such as porosity and incomplete fusion.Fatigue striations appear in the fatigue crack propagation zone, and a large number of equiaxed dimples are found in the instantaneous fracture zone.